mirror of
https://github.com/bitcoin-s/bitcoin-s.git
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c90f318fd7
* Refactor crypto module to be compatible with Scala.js * more changes * some more changes * abstract out Schnorr stuff * abstract out adapter stuff * cleanup * some more cleanup * fix build * Removed references to ECPoint outside of .jvm scope * remove references to ECPoint from the shared code * cleanup * remove cirlular dependencies * more cleanup * cleanup * move SipHash to CryptoContext * scaladoc * scalafmt Co-authored-by: nkohen <nadavk25@gmail.com>
93 lines
2.9 KiB
Markdown
93 lines
2.9 KiB
Markdown
---
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id: secp256k1
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title: Secp256k1
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---
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[Libsecp256k1](https://github.com/bitcoin-core/secp256k1) is used to preform cryptographic operations on the secp256k1 curve.
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This is the curve that bitcoin uses. There is a _signficant_ speedup when using this library compared to java crypto libraries
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like bouncy castle.
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In bitcoin-s, we support native binaries for libsecp256k1
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1. [linux 32 bit](../../secp256k1jni/natives/linux_32)
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2. [linux 64 bit](../../secp256k1jni/natives/linux_64)
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3. [mac osx 64 bit](../../secp256k1jni/natives/osx_64)
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4. [windows 64 bit](../../secp256k1jni/natives/windows_64)
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Bitcoin-s uses a zero dependency library called [`native-lib-loader`](https://github.com/scijava/native-lib-loader).
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That does the appropriate loading of the library onto your classpath to be accessed.
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### Using libsecp256k1
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To tell if you have access to libsecp256k1 you can do the following
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```scala mdoc:invisible
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import org.bitcoin._
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import org.bitcoins.crypto._
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```
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```scala mdoc:compile-only
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val isEnabled = org.bitcoin.Secp256k1Context.isEnabled()
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println(s"Secp256k1Context.isEnabled=${isEnabled}")
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```
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If libsecp256k1 is enabled, you can use [NativeSecp256k1](/api/org/bitcoin/NativeSecp256k1)
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with static method defined in the class.
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```scala mdoc:compile-only
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val privKey = ECPrivateKey.freshPrivateKey
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val pubKey = privKey.publicKey
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val dataToSign = DoubleSha256Digest.empty
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val signature = NativeSecp256k1.sign(dataToSign.bytes.toArray, privKey.bytes.toArray)
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val verify = NativeSecp256k1.verify(dataToSign.bytes.toArray, signature, pubKey.bytes.toArray)
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println(s"Verified with NativeSecp256k1 signature=${verify}")
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//you can also just directly sign with the ECKey interface:
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val signature2 = privKey.sign(dataToSign)
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val verified2 = pubKey.verify(dataToSign, signature2)
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println(s"Verified with NativeSecp256k1 again=${verified2}")
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```
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### When libsecp256k1 isn't available, or you want to turn it off
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There are two reasons you wouldn't want to use libsecp256k1
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1. You don't trust the pre-compiled binaries we are using
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2. Your OS/arch is not supported
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There are two ways you can circumvent libsecp256k1
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1. Set `DISABLE_SECP256K1=true` in your environment variables. This will force `CryptoContext.default` to return false which will make Bitcoin-S act like `Secp256k1Context.isEnabled()` has returned false.
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2. Call Bouncy castle methods in `ECKey`.
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Here is an example of calling bouncy castle methods in `ECKey`
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```scala mdoc:to-string
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val privKey = ECPrivateKey.freshPrivateKey
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// calls bouncy castle indirectly via CryptoContext
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val publicKey = privKey.publicKey
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val dataToSign = DoubleSha256Digest.empty
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// calls bouncy castle indirectly via CryptoContext
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val signature = privKey.sign(dataToSign.bytes)
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// calls bouncy castle indirectly via CryptoContext
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val verified = publicKey.verify(dataToSign.bytes, signature)
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println(s"Verified with bouncy castle=${verified}")
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```
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### Building libsecp256k1
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[See instructions here](add-to-jni.md#adding-to-bitcoin-s)
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